Electron tube



June 14, 1949. DR|E$HMAN ET 2,472,942

ELECTRON TUBE Filed March 18, 1947 s Sheets-Sheet 1 INVENTORS I DONALD DR/ESCHMAN BY RICHARD CHAMEERL //v ATTORNEY D. DRIESCHMAN ET AL ELECTRON TUBE June 14-, 1949.

s Sheets-Sheet 2 Filed March 18, 1947 IN VEN TORS DR/ESCHMAN DONALD RICHARD 67/ BY].

A 55?; IN

ATTORNEY I June 14, 1949.

D.- DRIESCHMAN ETTAL ELEc'rRon TUBE 3 Sheets-Sheet 5 Filed March 18, 1947.

v INVENTORS v DONALD DR/ESCHMAN BY Q0/1420 CHAMZERL/N ATTORNEY Patented June 14, 1949 ELECTRON TUBE Donald Drieschman, Los Altos, and Richard Chamberlin, San Bruno, Calif., assignors to Eitel-McCullough, Inc., San Bruno, Calif., a corporation of California Application March 18, 1947, Serial No. 735,466

4 Claims.

Our invention relates to electron tubes, and more particularly to improvements in the electrode arrangement and envelope structure of such tubes.

It is among the objects of our invention to provide an electron tube of small physical size yet capable of producin a relatively large amount of power in the higher frequency ranges.

Another object is to provide a sectional envelope structure fused together at a metal-to-metal joint, whereby assembly of the tube is facilitated.

Another object is to provide a sectional envelope of the character described in which the lower section embodies an improved header and contact prong structure.

Still another object is to provide a tube construction which has special advantages in connection with multi-grid tubes such as tetrodes.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of our invention. It is to be understood that we do not limit ourselves to this disclosure of species of our invention, as we may adopt variant embodiments thereof within the scope of the claims.

Referring to the drawings:

Figure 1 is a vertical sectional view of a tube embodying the improvements of our invention, taken in a plane indicated by line I l of Figure 2; and

Figure 2 is a bottom view of the same.

Figure 3 is a vertical sectional subassembly view of the lower envelope section with the oathode only mounted in position, taken in a plane indicated by line 3-3 of Figure 4; and

Figure 4 is a top view of the same.

Figure 5 is a vertical sectional subassembly view of the lower envelope section with the cathode and control grid mounted in position; taken in a planeindicated by line 55 of Figure 6; and

Figure 6 is a top view of the same.

In terms of broad inclusion, our tube comprises a-lower envelope section having a metallic ring and a disk-like vitreous header sealed to the ring, an upper envelope section having a metallic ring fitted to the ring of the lower section, a fused metallic bonduniting the rings, a contact prong sealed to the header, and an electrode connected to the prong. In our preferred tube structure an anode issupported on the-upper section and a cathode and control grid are connected to prongs sealed to the header. In our tetrode type of tube a screen grid is also provided and is connected to one'of the envelope rings.

In greater detail, and referring particularly to Figure 1 of the drawing, our invention is illustrated by an external anode tetrode structure comprising an envelope having an upper section generally designated by numeral '2 and a lower section generally designated by numeral 3, which evelope sections are united at a joint 4. The upper section is made up of a metallic ring 6, a cup-shaped metallic anode I and a tubular wall 8 of vitreous material sealed between ring 6 and a flange 9 0n the anode, By this arrangement anode 1 is supported on the vitreous wall 8 of the upper envelope section. The tube is preferably exhausted through a metal tubulation H on the anode, which tubulation is pinched off at tip 12.

Anode l is preferably of copper, and ring 6 and flange 9 are preferably of a lower expansion metal such as one of the iron alloys commonly used in making glass-to-metal seals. Wall 8 may be of any suitable vitreous material having insulating and vacuum-tight properties such as glass, ceramic or the like capable of being sealed or bonded to the metallic members. Ring 6 has a cross section of inverted L-shape, including a downturned flange l3 and an inturned flange M, the latter flange being preferably of channel-shape to provide an annular depression in which wall 8 is sealed. This particular shape permits ring 6 to be made of relatively thin material, yet with sufiicientrigidity to maintain a good seal with vitreous wall 8.

Lower envelope section 3 is made up of metallic ring l5 and a disk-like header it of vitreous material sealed to the ring. Ring l5 has a cross section of inverted U-shape, including a downturned outer flange l1 and an inner flange l8, the latter preferably having an inturned lip I9 for added strength at the seal. As seen in Figure 1, ring I5 is fitted within ring 6 of the upper section so that downturned flange l3 overlaps the outer flange IT. The two envelope sections are united by a fused metallic bond at joint 4, as by a weld or braze along the lower registering edges of the ring flanges. Since header H5 is sealed only to the inner flange of the U-shaped ring [5, the braze or weld at joint 4 may be made without danger of cracking the header.

With the sectional envelope structure above described the two envelope sections may be separately fabricated and the various electrodes located in position prior to closing up the envelope. After all internal parts have been mounted, the tube is finally assembled by merely inserting the upper section over the lower section and securing the two together at joint 4.

The internal electrodes of our preferred tube comprises cathode 2!, control grid 22 and screen grid 23. These are tubular electrodes projecting into anode l. The two grids have upper free ends and lower fixed ends and are preferably made with vertical wire bars, the screen grid being preferably capped by a top piece 24. Screen grid 23 is supported from its lower end by a bracket 25 fastened to a flange 39 secured to the inner flange H? on ring 15 of the lower envelope section. By this arrangement the united rings 6 and I provide a terminal for the screen grid in the final tube.

The remaining electrodes are connected to and supported by rigid contact prongs sealed to header 16. As shown in Figures 1 and 2, a plurality of prongs 26, 21, 28,;29, 3i, 32, 33 and- 34 are arranged in a circle around a center prong 35. All these prongs are rigid rods adapted to be plugged into a socket. preferably of heavier stock to give added support for the tube in the socket, and preferably carries an enlarged piece 31 having a guide key 33 for indexing the surrounding prongs in the socket.

Control grid 22 is connected to center prong 35 by a supporting bracket 39, which bracket is preferably of U-shape brazed at the center to the top of prong 36 and at the ends to opposite sides of grid band 4!. This structure is best illustrated by the subassembly view in Figure 5. It will be seen that control grid terminal prong 353 is located centrally of screen grid terminal ring 6-15, which means that the terminals of these two are coaxially arranged. Such an arrangement is particularly desirable in circuits for higher frequency operation employing coaxial lines.

The indirectly heated cathode 2| comprises a cylindrical core 42 of metal, preferably cupshaped, carrying a coating 43 of suitable electron emissive material. A coating of barium and strontium oxides, commonly used in cathodes of this type, may be employed. A tubular skirt 44 on the cathode core is mounted by a bracket having four fingers 48 secured to prongs 21, 29, 32 and 34. These four prongs, all connected to the cathode, provide good support and ample current carrying path. The cathode heater 41 is a coil of resistance wire mounted on conductors 38 extending through an insulator 49 and connected by tabs 5! to prongs 28 and 33. Figure 3 shows the cathode and heater in mounted position on the lower envelope section.

A capsule 52 of getter material such as magnesium is preferably connected by wires 53 to prongs 26 and Si (see Figure 4). This getter is flashed during exhaust of the tube in the usual manner for the purpose of absorbing residual gases. As shown in Figure 5, a strap 54 is preferably connected between prong 26 and flange 39 so that prong 26 also serves as a screen grid lead, in event it is desirable to use a contact prong instead of the grid terminal ring. After the getter is flashed the opposite prong 35 serves no other useful purpose and therefore is merely a fabricating prong.

Instead of using an indirectly heated cathode, the cathode may be of the conventional filamentary type, in which case the two ends of the filament would be connected to a pair of contact prongs in a manner similar to the cathode heater coil illustrated. It is also understood that a conventional type of internal anode may be used instead of an external anode. We prefer the The center prong is 4 external type of anode however, because of the increased heat dissipation properties.

Our improved tube has many advantages. The tube structure enables it to be built in small physical sizes. The tube illustrated can be made with an overall height of not over 2 inches and yet having an anode dissipation capability of several hundred watts. Because of the improved structure and terminal arrangement the tube is capable of operation in the higher frequency ranges, say up to 500 megacycles.

One of the important features of our tube is the sectional envelope construction wherein the cathode and grids are all mounted on the lower section 3 prior to making the final braze at joint 4. The generally fiat lower section keeps the cathode and grid structures out in the open where they can be readily worked on during assembly as illustrated in Figures 3 and 5. The upper generally cup-shaped envelope section 2 may then be simply inserted over the electrode assemblies and brazed in place.

We claim:

1. An electron tube comprising a lower envelope section having a metallic ring and a disk-like vitreous header sealed to said ring, an upper envelope section having a metallic ring fitted to the ring of the lower section, a fused metallic bond uniting said rings, a plurality of Contact prongs sealed to the header, one of said prongs being disposed centrally of the rings, a control grid electrically connected to the center prong, a cathode electrically connected to another pron and a screen grid electrically connected to on of said rings.

2. An electron tube comprising a lower envelope section having a metallic ring and a disk-like vitreous header sealed to said ring, an upper envelope sectionhaving a metallic ring and a vitreous wall sealed to the last mentioned ring, said rings having registering edges, a fused metallic bond uniting said edges, an anode supported on the vitreous wall of the upper section, a plurality of contact prongs sealed tothe header, one of said prongs being disposed centrally of the rings, a control grid electrically connected to center prong, and a cathode connected to another prong.

3. An electron tube comprising a lowerenvelope section having a metallic ring and a disk-like vitreous header sealed to said ring, an upper envelope section having a metallic ring and a vitreous wall sealed to the last mentioned ring, said rings having registering edges; a fused metallic bond uniting said edges, an, anode supported on the vitreous wall of the upper section, a plurality of contact prongs sealed to the header, one of said prongs, being disposed centrally of the rings, a control grid electrically connected to center prong, a cathode connectedto another prong, and a screen grid electrically connected to one of said rings.

4. An electron tube comprising a lower envelope section having a metallic ring and a disk-like vitreous header sealed to said ring, an upper envelope section having a metallicring and a vitreous wall sealed to thelast mentioned ring, said rings having registering edges, a fused metallic bond uniting said edges, 9'. cup-shaped metallic anode supported on the vitreous wall of the upper section, a plurality of contact prongs sealed to the header, one of said prongs being disposed centrallyof the rings, acontrol gridelectrically connected to the center prong, a cathod electrically connected to another prong, and a, screen grid connected to one of said rings.

DONALD DRIESCHMAN. RICHARD CHAMBERLIN.

REFERENCES CITED The following references are of record in the file of this patent: 

